My guess is she didn’t use government Email servers for these communications. The servers could be free anonymous accounts if that’s the case. The key is finding out what the email address was. If it can be identified there’s a chance the emails are backed up by the hosting company. Her computer identified her account so it had to go...
The IP address of her computer, or office at a minimum, would likely be known. That IP address could be searched for in the various free hosting companies and that could expose her Email account(s) and then the Emails.